Processing of rayon packages



Patented Nov. 22, 1949 James W. Jacokes, Ashevifle: G,, :assignor to American Enka Corporation, Enk-a, N.- C,, acorporation of De1awar'e No Drawing. Application August 12,

fieriarlflo. 6961;072

1 Claim. (01. 3-4375?) The present invention relates to the aftertreatment .of viscose rayon packages and .more particularly to a method of inhibiting the formation of dark spots normally occurring .in :those areas defined by the surfaces of therayon .packages during the aftertreating thereof.

Broadly, the invention is concerned with the treatment of any type of package formed from freshly spun viscose rayon and having a low degree of permeability. However, the invention is concerned primarily with those types of packages that are wound on rigid, perforated bobbins and thereby acquire a low degree of permeability.

'It'is the usual practice to wash and desu'lphurize such acid rayon spools or packages 'by forcing suitable 'treating'liquids through the body thereof by the application of a pressure differential to the liquids. The procedure generallyadopted is to vacuum and/orpressure wash .the acid spools with water at room temperature to remove all of the acid and spinbath salts present ,as aresult of passing the thread through an acid coagulating bath during the thread manufacturingv stage. This-washing stepis followed bya s'horft hot water wash to remove the carbon 'bisulphide and this is known as the degassing operation. The-spools are next treated with a dilute solution .of ammonium sulphide or sodium sulphide in order .to remove the sulphur content and are finally washed with water to remove the desu'lphuring liquid.

One of the major difficulties encountered in washing and desulphuriz'ing viscose rayon in package form is due to the presenceof certain impurities within the .acid thread. Theseimpurities originate in the constituents used in the manufacture of the thread and during the usual liquid treatments most of them remain distributed substantially uniformly throughout the packages. However, a small quantity of the impurities follow the direction of flow of the treating "liquids and form dark spots near the surfaces of the packages. If the fiow of liquid is :fromthe outside to the inside of the package the dark spots will be near the inside surface whereas if the flow trom the inside to the outside then the *da-rk spots will occur near the outside surface of the package.

Prior to the present invention, :it has been necessary to preclean a substantial amount of the thread, i. e., several hundred yards-oi thread-containing these dark spots have been removed and could be sold only as inferior quality. It is obvious that this precleaning step is time and labor consuming to carry out and is therefore doubly expensive in the process because the inferior thread must besold at a considerably low rpriee than it would otherwise demand. t it is therefore an object of the present invention to prevent or inhibit the'tormation :of dark spots in freshly spun packages of viscose rayon.

A further object of this'invention is to provide a process :of liquidtreatingbobbin sp'u-n rayon packages by means of applying a pressure difter entiafto the liquids to torceth'e .same through the packages and, during the- :liquid treatments, subjecting the packages to the :action of a special aikalli base or salt to fix 'theztroublesome impurities throughout the body .of the packages.

an additional object of the present invention is to treat rayon packages of low permeability with-a dilute solution of ammonia, or :an iailkal'i sall tadapted tor the purpose, prior to the .desulphurizing .step whereby the formation of dark spots at thesurtace of the packages is inhibited. Qther object'srand advantages of this invention will become apparent from a consideration of the following detailed description.

It has now been determined that if a treatment witha special alkaliorsalt solution is given to the viscose rayon packages after they have been was'hed-acid-free with *water at *room temperature, but prior to the desulphurizing step, then the impurities are fixed in the pack-age uniformly throughout all portions thereof, and upon subsequent "desulphurizing' the formation of dark spots at-the surface of the'package has been substantially prevented. The normal aftertre'a ting steps as heretoforementioned; namely, -washing, degassing or removing the carb-on-bisulphide-with hot water, desulphuriz-ing rand rewashing with water, .are all used in the ,present process, .andin addition the special treatment .with an alkali base or salt is injected. The special treatment is preferably given after the degassing treatment with hot water, in which case, the special treat-j ment mustbe followedbya short hot water wash. prior to desulphur'izing. However, the dark spots can also be inhibited by giving the special treatment after the acid-free washing and just prior to the hot Water'degassingoperation. .In either case, the special "treatment must be effected at some stage after the package is washed acid-free and prior to desulphuriz'ing;

Probably the most practical chemical iromthe standpoint of economy and efiec'tiv-eness which can be used this-process isammoriiain =solution, although it has been determined that sodium carbonate, sodium bicarbonate and ammonium acetate are also effective to prevent the formation of dark spots at the surface of the package. The concentration range of these chemicals in the solution is from 0.01% to 2.0%, about 0.4% usually being sufiicient. Higher concentrations, of course, can be used but no additional advantages seem to be gained from such higher concentrations. The temperature range for the special solution is from 10 C. to 45 C., and preferably between 20-30 C. The temperature range for the subsequent hot water wash is from 40 C. to 80 0., preferably 60-70 C.

The concentration of the special solution and the length of time that the packages are treated depend to a large extent upon the permeability of the packages and the pressure differential applied.

In the following examples taken from actual tests, the packages wound on spools had permeabilities ranging from 10 to 30 cc. per spool per minute. A vacuum of approximately 15 inches was applied to the inside of the spools during each of the washing treatments. In this so called "vacuum wash dark spots, without the special treatment, normally occurred near the inside surface of the packages.

Example 1 One tank load of acid spools was washed for 12 hours with water at 27 C. until the spools were acid-free. This was followed by a hot water wash at 65 C. for 1 /2 hours to remove all of the carbon bisulphide. In order to inhibit the formation of dark spots, the spools were washed with a 0.4% ammonia solution (calculated at NHs) at 27 C. for one hour, followed by a hot water wash at 65 C. for one hour. The spools were desulphured subsequently by a treatment with a desulphuring solution containing 0.4% ammonium sulphide for four hours at 32 C. After this the spools were washed with hot water at 65 C. for about hours. The washed and desulphured spools were free from dark spots.

Example 2 One tank of acid spools was washed for 12 hours with water at 27 C. until the spools were acidfree. In order to inhibit the formation of dark spots, the spools were washed for one hour with a 1.0% ammonia solution (calculated at NH3) at 27 C. This was followed by a hot water wash at 65 C. for 1 hours to remove carbon bisulphide. Finally, the spools were desulphured and rewashed in the same way as for Example 1. The washed and desulphured spools did not contain the usual dark spots.

Example 3 One load of acid spools was washed for 12 hours with water at 27 C. until acid-free. Next, they were given a hot water wash at 65 C. for 1 hours to remove the carbon bisulphide. In order to inhibit the dark spot formation, the spools were washed with a 0.1% sodium bicarbonate solution for 2 hours at 27 C.; this was followed by a hot water wash at 65 C. for one hour. The spools were desulphured and rewashed the same as for Example 1. The spools were practically free from dark spots.

Example 4 One tank of acid spools was washed for 12 hours with water at 27 C. until acid-free. The spools were degassed by a hot water wash at 65' C. for 1 hours. In order to inhibit the formation of dark spots, the spools were given a wash with a 0.5% ammonium acetate solution for two hours at 27 C., and a hot water wash for one hour at 65 C. This was followed by desulphuring and rewash treatments which were the same as for Example 1. The washed and desulphured spools were free from dark spots.

Example 5 One load of acid spools was washed for 12 hours with water at 27 C. until acid-free. Next, they were given a hot water wash at 65 C. for 1 /2 hours to remove the carbon bisulphide. In order to inhibit the dark spot formation, the spools were washed with a 0.1 sodium carbonate solution for 2 hours at 27 C.; this was followed by a hot water wash at 65 C. for one hour. The spools were desulphured and rewashed the same as for Example 11 The spools were practically free from dark spots.

In the foregoing specification, when reference is made to initially washing the packages or spools acid-free, it is meant that after the washing treatment no acid reaction occurs with methyl orange indicator, and on analysis of the thread, less than 0.02% acid is present.

In the claim, near one surface means near either the inside surface or the outside surface of the package, depending on the direction of flow of the treating liquids.

What is claimed is:

In a process of aftertreating freshly spun packages of viscose rayon wound on rigid, perforated bobbins under sufficient tension to acquire a low degree of permeability ranging from 10 to 30 cc. per bobbin per minute wherein liquids are forced through the packages by means of an applied pressure differential and involving the steps of washing the packages with water at room temperature until they are acid-free as determined by the methyl orange test, degassing with hot water maintained in a temperature range of 40 to C., desulphurizing With an alkali sulphide and rewashing with hot water, which steps normally resulting in the formation of 'dark spots near one surface of each of the packages, the improvement that consists essentially of treating the packages subsequent to the acid-free washing but prior to the desulphurizing with a dilute solution of ammonia in a concentration range of 0.01% to 2.0%, the solution being maintained in a temperature range of 20 C. to 30 C. whereby the formation of dark spots near one surface of each of i the packages is inhibited.

JAMES W. JACOKES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,802,935 Banigan Apr. 28, 1931 2,074,076 Schrenk Mar. 16, 1937 2,237,844 Ridgway Apr. 8, 1941 OTHER REFERENCES Amer. Dyestufi Rep., Mar. 8, 1948, page P162. 

